I think you are definitely headed in the right direction by vertically bi-amping. I don't know what your system configuration is but if you can get your amps close to the speakers and use as short a speaker cable as possible will also show additional benefit. Almost as much improvement as going to bi-amping.
I also agree with the others about perhaps needing some more juice. I would be worried about the bottom end potentially clipping. Beyond that, there is a definite sonic improvement when your amps have lots of headroom and current to spare. I bet if you where to get a pair of 250.5's you would be quite surprised at the improvement in depth and clarity. That's not to say there is anything wrong with your Alephs, but just think what they could sound like if they were only driving the mids and highs. Your B&W's are similar to mine and Beemer's Aerials and we know how much these can open up with the addition of more quality power.
Another thing you could try is to keep the Alephs on the tops and get a more powerful Pass amp to run the bottom end. Yea, I know, I'm just spending your money. :)
I also agree with the others about perhaps needing some more juice. I would be worried about the bottom end potentially clipping. Beyond that, there is a definite sonic improvement when your amps have lots of headroom and current to spare. I bet if you where to get a pair of 250.5's you would be quite surprised at the improvement in depth and clarity. That's not to say there is anything wrong with your Alephs, but just think what they could sound like if they were only driving the mids and highs. Your B&W's are similar to mine and Beemer's Aerials and we know how much these can open up with the addition of more quality power.
Another thing you could try is to keep the Alephs on the tops and get a more powerful Pass amp to run the bottom end. Yea, I know, I'm just spending your money. :)